Signal translating apparatus and supporting means therefor



NOVUZZ, 1949 c, slNNETT 2,488,608

SIGNAL TRANSLATING APPARATUS AND SUPPORTING MEANS THEREFOR Original Filed Oct. 9, 1941 i /4 I I7 I0 "1 Q 2 0 $1 3nventor a? EHESTER MSINNETT v .I B\ I: 3 50 760 7,000 I 'Feipui/vcyfc' 2 5 (I ttormg Patented No 22,1949

. SIGNAL TRAN SLATING APPARATUS AND SUPPORTING MEAN S THEREFOR Chester M. Sinnett, Westmont, N. J., assignor to Radio Corporation of America, a corporation of Delaware Original application October 9, 1941, Serial No. 414,305, now Patent No. 2,376,456, dated May 22, 1945. Divided and this application May 30, 1944, Serial No. 538,073

paratus, and more, particularly to a mounting fora signal translating device for use especially in connection with phonograph records, the present application being a division of my copending application Serial No. 414,305, filed October 9, 1941, now Patent No. 2,376,456, granted May 22,

In my aforesaid copending application, I have disclosed a capacity type pickup, the capacity of which is varied in accordance with the record groove modulation of a phonograph record to provide frequency modulation in an oscillator circuit wherein the pickup constitutes a tuning element. The pickup is, carried on the end of a pickup arm which is arranged for swinging movement over a record in customary manner.

Ihe pickup arm arranged as above set forth usually exhibits low frequency resonance. If the pickup is rigidly mounted on the arm, then the pickup arm resonance introduces distortion in the reproduced signal, particularly where, as in the case of the pickup disclosed in my aforementioned oopending application, the operating parts have a low mechanical impedance and the needle pressure of which is very low on the record.

The primaryobject of my present invention is to provide an improved pickup mounting on the pickup arm by means of which distortion due to low frequency pickup arm resonance will be reduced to a minimum.

. More particularly, it is an object of my present invention to provide an improved pickup mounting which will serve effectivelyto isolate vibrations of the pickup arm, particularly at the low resonant frequency thereof, from the pickup.

Another object of my present invention is to provide an improved pickup mounting as aforesaid which is relatively stiff torsionally, so that resonant torsional vibration will not be imparted to the pickup. I

Still another object of my present invention is to provide a pickup mounting as above set forth which is very simple in construction, inexpensive in cost, and highly efficient in use.

In accordance with my present invention, the pickup unit is mounted in av suitable heador frame to each side of whichis secured a flat spring of phosphor bronze or the like. The springs extend from the frame in parallel relation and straddle the free end of the pickup arm, being secured to the pickup arm at their, opposite ends. The springs are so disposed that they extend in parallel planes normal to .a plane transversely through the pickup arm, and they 12 Claims. (01. 274-44) maintain the pickup head or frame in spaced relation to the pickup arm. Flat springs are employed so that the unit will be still torsionally. However, the pickup unit is yieldably mounted in a direction transverse to the pickup arm, and therefore vibration of the arm due to swinging movement thereof over the record will be very greatly attenuated and will not materially affect the pickup. The connecting springs are preferably damped by securing thereto, at appropriate points, a damping material having suitable damping characteristics. With an arrangement of this sort, the system may be made to cut off at a frequency considerably above the low frequency resonant frequency of the pickup arm.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention, itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description of one embodiment thereof, when read in connection with the accompanying drawing, in which I Figure l is a side elevation of a pickup mounted on a pickup arm in accordance with one form of my-present invention,

. Figure 2 is an enlarged, top plan of the forwardendof the pickup arm, the pickup unit, and the mounting therebetween,

' Figure 3 is a side elevation, partly in section, of the structure shown in Fig. 2, and

Figure 4 is a set of curves showing the resonance'of the pickup under various conditions both with and without a mounting according to the present invention.

Referring more particularly to the drawing, Whereln'similar reference characters designate corresponding parts throughout, there is shown a pickup arm I pivotally mounted on a horizontal pivot 3,which is formed on the upper end of a. yoke 5 having a downwardly extending, vertical pin or post I received in the vertical bearing 9 of a standard II. By reason of the pin or post 1 in the bearing 9, the arm I is free to swing in a horizontal plane over a phonograph record (not shown) At the same time, the arm I is free to swing in, a vertical plane on the horizontal pivot 3.

-A pickup device l3, preferably but not necessarily of the capacity type such as that disclosed and claimed more particularly in my above identified copending application, is clamped in a head or frame 15 by a plurality of'screws l'l. The

pickup l3 includes a needle l9 adapted to cooperate with and to be vibrated by the modulated groove of a phonograph record to thereby set up signal voltages. The, head or, frame. [5. is. secured to the arm I by means of a pair of leaf springs 2| of phosphor bronze or the like. The springs 2| are secured adjacent one end to thehead 15 and extend therefrom in parallel relation. As will be seen from Fig. 2, the. springs; 21 straddle the forward or free end of the pickup arm l and their opposite ends, are securedto, a pair of blocks 23 carried by the, pickup arm I- The springs 2| are disposed in planes parallel to a plane which extends transversely through the pickup arm I and they maintain the heady I 5 in spaced relation to the adjacent. end of the arm I. Thus, it will be apparent that the head and the pickup l3 are yieldably mounted for movement in a direction transversely of the arm I-, that. is, in a plane parallel to the plane of the record. At the same time, since the-leaf springs'2 l are disposed in planes normal to this transverse. direcs tion, they are relatively stiff torsionally. Preferably, although not necessarily, a pair of; strips or blocks of damping material 25 are securedjat their-ends to the springs 21 by a suitable adhesive- 21. The damping members 25 extend between the pickup frame or head I5 and the blocks 23 and: are shown mounted on the inside surface ofeach of the blades 2|. However, it isv apparent that the damping blocks 25 may be mounted on theoutside surfaces of'the springs 21 and may or may not engage the spring blades 2 I' along the entire lengths thereof, as may be found most suitable. The damping members 2-5 are pref.- erably made of a material having relatively reat molecular inertia, such as printers r011, Glyptal, DuPont Viscoloid, or the like.

Fig; 4 shows three sets of curves X, Y and representing the resonance of the system described above under various conditions. The: curve X shows that the low frequency vibration of a system wherein the pickup is rigidly mounted on. the pickup arm is quite high. The vibration of a system wherein the pickup head I5 is mounted on the pickup arm I by means of thesprings 2| alone is shown by the curve Y. Here, it wiib be seen that there is a fairly sharp peak inthat region of about 60 cycles. Byv adding the damping strips 25 on the springs 21', the resonance of. the system is changed to that shown by. the curve Z, from which it will be noted that there is a smaller peak at about 80 cycles and that. at the extreme, low frequency end, the response. drops way down. Thus, with a mounting of the type above-described, it is possible'to provide a: system. which will have a resonant peak in theregion of around 80 cycles per second and' below which the response falls off rapidly. Since the tonearm swinging resonance is usually in the region'- of about 15 to cycles, it is apparent that, with animproved mounting according to my present invention, the low frequency vibrations of the; pickup arm will not be transmitted to thepickup and the distortion normally introduced thereby will be eliminated.

Although I have shown and described: butone embodiment of my present invention, it will undoubtedly be apparent to those skilled in the artthat many other modifications thereof, as well as: changes in the particular one described above, are possible. I therefore desire that my-inven tion shall not be limitedexcept insofar as'is madenecessary by the prior art and by the spirit of the appended claims.

:inga, resilient element secured to each of said arm and said device, and a damping element carried by said resilient element, said damping element having the characteristic of possessing relatively great molecular inertia.

3. In signal translating apparatus, the combination ofi asupporting arm, a signal translating derice. including a needle adapted to cooperate, with a; phonograph. record, means coupling said' deviceztorsaid arm, said coupling means comprising a. pair of flatv springs secured to said device in parallel relation and straddling said arm, said springs being also secured to said arm, and a pair of damping strips secured one to each of saidsprings, said damping. strips being formed of a material possessing relatively great molecular inertia;

4.v In. signal. translating apparatus, the combinationcof a supporting arm, a signal translatingdevice includingv a needle adapted to cooperate with: a phonograph record, means coupling said device. tozsaid arm, said means comprising a pair of flatspm'ng elementssecured to said device and extending therefrom in spaced relation, said springs straddling said supporting arm in spaced relation. thereto, means connecting said springs to.- said supporting arm, and damping means secured to. each of saidsprings.

5; In: signal translating apparatus, the combination of" a supporting member, means mountingrsaid. supporting member for movement in a plane across-aphonograph record, a signal translating device adapted to'cooperate with the record, and a. pair ofyieldable elements each secured at oneend to -said device and'at its opposite end to saidisupporting member, said yieldable elements maintaining said device in spaced relation to said supporting member and being yieldable in a direction transverse to said supporting memberand' parallel to said plane whereby said device isyleldinglycarried on said supporting member for movement relative thereto as a whole transversely of said supporting member.

61 Signal. translating apparatus according to claim 5 characterized-in that said yieldable elemerits comprise spring members.

7. Signal translating apparatus according to claim 5 cliaracterized in that said yieldable elements comprise leaf springs arranged in planes normaltosaid'transverse-direction.

8. Signal translating apparatus according to claim 5 characterized in; that saidyieldable elements=comprise leaf springs one on each side of said device and said supporting member, and characterized further in' that said springs are arranged inplanes normal to said transverse directlom 9; Signal translating apparatus according to claim 5 characterizedbythe addition of damping means in association with said yieldable means ftu damping oscillations thereof;

10. In signal translating apparatus, the combination of a supporting arm, means mounting said supporting arm for movement in a plane across a phonograph record, a pickup device adapted to cooperate with the record, a pair of leaf springs disposed one on each side of said arm and said pickup device yieldably connecting said device to said arm in spaced relation to each other, said springs being disposed to permit relative motion between said device and said arm in a direction transverse to said arm and parallel to said plane, and vibration damping means secured to each of said springs, said damping means being formed of a material having relatively great molecular inertia.

11. Signal translating apparatus according to claim wherein said damping means is carried solely by said springs.

12. In signal translating apparatus for phonographs, the combination of a supporting arm, means mounting said supporting arm for movement in a plane across a phonograph record, a signal translating device including a needle adapted to cooperate with the record, and a pair of yieldable elements each secured at one end to said device and at its opposite end to said supporting arm, said yieldable elements maintaining said device in longitudinally spaced relation to said supporting arm and being yieldable in a direction transverse to said supporting arm and parallel to said plane whereby said device is yieldingly carried on said supporting arm for movement relative thereto as a whole transversely of said supporting arm.

CI IESTER M. SINNETT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

